1. Technical Field
This invention relates to chairs and, more particularly, to an adjustable chair adaptable to a size of a user's thighs.
2. Prior Art
Various types of backrests are known, including fixed backrests, inclined backrests for support of the lumbar region of the back, and height adjustable backrests. Also known are car seats and the like that are fitted with equipment to move the whole seat such as glide rails or the like. Certain office chairs are also known to be capable of adjusting their lumbar support region.
A conventional task chair has a standardized seat depth of approximately 40 to 43 cm. There is sufficient space on the seat surface for a person's buttocks and, depending on the size of the person sitting on the chair, a variable length of the thigh. For shorter persons, the front edge of the chair is often too far forward, so that the blood vessels in the legs are compressed by the front edge, thus hindering the blood supply to the legs. The unpleasant and unhealthy consequences are cold feet and varicose veins. To correct the seat depth, in some task chairs, the position of the backrest is adjustable; that is, the person sitting in the chair can choose how great the distance between the front edge of the chair and the backrest should be. However, if the seat surface is physiologically shaped, then a shorter person sits too far forward or a tall person sits too far to the rear on the seat surface.
A seat depth adjustment for motor vehicle seats is known in the prior art. In it, the seat region at the front of the seat is movable in the longitudinal direction of the vehicle. The front seat region is secured to the seat by two parallel retaining arms, which can be swiveled about a horizontal shaft fixed to the seat. Its top side is located partly under the seat surface. The retaining arms are articulated in the rear end of the moveable seat region, and an adjustable-length arm is pivotally secured to the seat at a rear shaft and articulated to the front end of the seat region. A disadvantage of this seat depth adjustment is that the retaining arms and the adjustable-length arm require shafts secured to the seat, which are disposed below and at a distance from the seat surface. Such a construction is unacceptable for task chairs for use in the office, because these arms under the seat surface are not only unattractive but do not guarantee enough space for the legs below the seat surface
Accordingly, a need remains for an adjustable chair in order to overcome the above-noted shortcomings. The present invention satisfies such a need by providing an adjustable chair that is easy to use and adjust, durable in design, provides sufficient thigh support to people of various lengths, and improves productivity. Such an adjustable chair prevents the circulation to a person's legs from being cut off, thus preventing the formation of varicose veins. The adjustable chair can advantageously be used in a variety of business settings, as well as in commercial vehicles, such as trucks and busses.